#include <bits/stdc++.h>
using namespace std;
int m,q,n,ans,l,r,u,v,ct[200005],now[200005],ok,a[200005];
int main(){
ios::sync_with_stdio(false);
cin >> n >> m >> q;
for (int i=1;i<=n;i++){
cin >> a[i];
}
for (int i=1;i<=q;i++){
cin >> u >> v;
ct[u]=v;
}
l=1; r=0; ans=1e9;
while (l <= n && r <= n){
if (ok == q){
ans=min(ans,r-l+1);
if (now[a[l]] == ct[a[l]])
ok--;
now[a[l]]--;
l++;
}
else
{
r++;
now[a[r]]++;
if (now[a[r]] == ct[a[r]])
ok++;
}
}
if (ans == 1e9)
cout << "impossible\n";
else
cout << ans << "\n";
return 0;
}
